1. Field of the Invention
The present invention relates to a method of, and an apparatus for producing multi-dimensionally bent elongate articles, such as door sashes, various moldings for automobiles, and the like.
2. Description of the Prior Art
A multi-dimensional or complex bending machine for producing elongate articles having two- or three-dimensional curvature from continuously supplied elongate raw material is known, and disclosed e.g. in U.S. Pat. No. 4,391,116 issued on July 5, 1983. This known machine comprises a movable roller device including a pair of upper and lower bending rolls which are mounted on a rotary wheel by means of a universal joint mechanism. The rotary wheel is rotatably supported by a plurality of rollers mounted on a vertically slidable plate, and has gear teeth which are in mesh with gear teeth of the rollers. The vertically slidable plate mounts thereon a drive motor connected to one of the rollers for driving the rotary wheel, and is vertically slidably supported by a horizontally slidable plate. The horizontally slidable plate mounts thereon a second drive motor connected to the vertically slidable plate through a transmission mechanism, and is horizontally slidably supported by a pair of side frames. One of the side frames mounts thereon a third drive motor connected to the horizontally slidable plate through another transmission mechanism. The elongate material is supplied from stationary guide rollers, to be bent by the movable roller device multi-dimensionally.
With the above-mentioned structure of the known bending machine, however, the overall arrangement is very bulky and costly, and more importantly, it proved to be very difficult to effect an accurate multi-dimensional bending of the elongate material owing to the following reasons. Firstly, since the bending rolls are mounted on the rotary wheel by a universal joint mechanism, and are not properly restrained from an unintentional motion, and also due to the time lag resulting from the inertia of the bending rollers and the universal joint mechanism, an elongate material cannot be bent accurately into a desired curvature, and may sometimes be snapped particularly in case of a slender material having a low bending rigidity. Secondly, during the bending operation, the rollers supporting and in mesh with the rotary wheel are applied with the reaction torque from the material, so that a large motor has to be used to drive the rotaty wheel with a sufficient torque. This results in an increase in the weight and inertia of the rotary wheel and the vertically slidable plate so that the starting and stopping operations of these elements cannot be accurately controlled. Similarly, the horizontally slidable plate is heavy in weight and has a large inertia since it carries the vertically slidable plate and drive motor and transmission mechanism therefor, among which the vertically slidable plate itself carries the universal joint mechanism, rotary wheel and drive motor and transmission mechanism therefor. Thus the starting and stopping operations of the horizontally slidable plate, either, cannot be accurately controlled.
Another problem encountered with the known bending machine resides in the complexity of controlling the operation. More particularly, the bending is effected by controlling the machine by measuring the supplied length of the elongate material and on the basis of X-Y program including the vertical and horizontal sliding amounts of the movable elements. The program by which an accurate bending is effected is very complicated and difficult to prepare, and such a complexity is further enhanced when a three-dimensional bending is to be effected, or when it becomes necessary to axially twist the material depending upon the nature of the product.
Still another problem is that, even when the known bending machine is capable of processing continuously supplied elongate material, in order to cut the bent material into a predetermined length, the continuous supply of the material has to be interrupted during the period in which a movable blade member is moved to effect cutting and returned to its original position, so that a real improvement in the productivity cannot be achieved. There have been no proposals relating to an effective cutting device to which the bent material can be supplied continuously.